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Chemistry LibreTexts

5.3.1: Practice Half-Life

  • Page ID
    235943
  • Exercise \(\PageIndex{1}\)

    How many years does it take for 4.7 half-lives to pass for a sample of sodium-22?  The half-life of sodium-22 is 2.6 years..

    Answer

    12 years

    Exercise \(\PageIndex{1}\)

    How many half-lives have passed for a sample of gold-198 that is 3.4 weeks old?  The half-life of gold-198 is 2.7 days.

    Answer

    8.8 half-lives

    Exercise \(\PageIndex{1}\)

    If you start with 422 mg of calcium-47, how much will remain after 5.00 half-lives have passed?

    Answer

    13.2 mg

    Exercise \(\PageIndex{1}\)

    The half-life of sodium-24 is 15.0 hours.  If you begin with a sample that has 675 nCi of activity, what activity will remain after 3.75 days?  (Hint: how many half-lives have passed for the sample after 3.75 days?)

    Hint

    6.00 half-lives have passed.

    Answer

    10.5 nCi of activity remain

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